Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 60Get this manual
Timing Adjustments IMPORTANT: If link rod was disassembled, make sure that 1116" (17.5mm) dimension Is retained
7Connect timing light to No.1 spark plug lead
AWARNING
Before cranking engine, keep clear of propeller, as It may rotate8With eng in in neutralhold throttle lever so that id le stop screw is against stop, then crank engine with starter motor and ad just throttle primary pickup sc rew to align degrees ATDC throttle primary pickup mark on flywheel with timing pointerRet ighten nut on ad justment screw
aLink Rod -1116" (17.5mm)